The present invention relates to a method and equipment for supporting mobility in a telecommunication system.
The proportion of mobile workforce with portable computers is growing all the time. These mobile users need to access their computer networks from multiple locations. Besides ordinary local area networks, wireless local area networks (WLANs) have entered the markets enabling wireless access to computer networks. WLANs provide the ease of use as no cables are needed. Typically WLANs use radio frequency technologies; however, it is also possible to use e.g. infra-red connections. As cellular telecommunication systems, WLANs provide wireless connectivity using cells, called microcells. WLAN access is provided with WLAN adapters, which are implemented as PC cards in portable computers, ISA or PCI cards in desktop computers or integrated within hand-held computers.
There are many system settings involved when a terminal is accessing a wired or a wireless network. Typically needed settings are: connection method settings, dial-in settings, IP (Internet Protocol) settings and application settings. The connection method specifies the connection type, e.g. a direct network connection or a modem connection. Dial-in settings specify at least the access telephone number and dialing prefix, IP settings comprise the needed parameters for accessing IP networks and application settings set the parameters required by popular applications. Besides ordinary settings needed for accessing and using wired LANs, there are a number of WLAN specific settings that are different in various WLAN networks. For instance, different security keys and data rates may be used in different WLAN networks. Typically the settings need to be changed manually every time when the used network changes.
WLANs, as other wireless telecommunication systems, comprise support nodes providing access for mobile terminals to wired networks. In the WLAN these support nodes are typically called access points. Access points may be grouped into sub-networks and the sub-networks may form a logical network. Sub-networks are WLAN segments that belong to the same logical network but need different settings. Especially as different sub-networks typically have different IP address segments, TCP/IP (Transport Control Protocol/Internet Protocol) settings need to be changed every time the terminal moves from the area of one sub-network to another. When a terminal is connected to an access point in a first sub-network and the connection is changed to an access point of a second sub-network, it can be said that the terminal roams from the first sub-network to the second sub-network. WLAN users need to change the settings manually every time they want to access a different sub-network. Thus roaming between sub-networks (and also between logical networks) is cumbersome and requires user intervention. This takes time, often the terminal needs to be restarted. If the new access point is in a different logical network, the establishment of the connection takes even more time. As many users are not familiar with different network settings, they may need to contact IT (Information Technology) support persons for help.